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new 3fc99de9c0 Minor: improve GroupsAccumulator docs (#12501)
3fc99de9c0 is described below
commit 3fc99de9c0ed9b0d4debde82f013e4df68562441
Author: Andrew Lamb <[email protected]>
AuthorDate: Tue Sep 17 11:17:17 2024 -0400
Minor: improve GroupsAccumulator docs (#12501)
---
datafusion/expr-common/src/groups_accumulator.rs | 25 +++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/datafusion/expr-common/src/groups_accumulator.rs
b/datafusion/expr-common/src/groups_accumulator.rs
index 156e21d9ae..8e81c51d84 100644
--- a/datafusion/expr-common/src/groups_accumulator.rs
+++ b/datafusion/expr-common/src/groups_accumulator.rs
@@ -56,9 +56,32 @@ impl EmitTo {
}
}
-/// `GroupAccumulator` implements a single aggregate (e.g. AVG) and
+/// `GroupsAccumulator` implements a single aggregate (e.g. AVG) and
/// stores the state for *all* groups internally.
///
+/// Logically, a [`GroupsAccumulator`] stores a mapping from each group index
to
+/// the state of the aggregate for that group. For example an implementation
for
+/// `min` might look like
+///
+/// ```text
+/// ┌─────┐
+/// │ 0 │───────────▶ 100
+/// ├─────┤
+/// │ 1 │───────────▶ 200
+/// └─────┘
+/// ... ...
+/// ┌─────┐
+/// │ N-2 │───────────▶ 50
+/// ├─────┤
+/// │ N-1 │───────────▶ 200
+/// └─────┘
+///
+///
+/// Logical group Current Min
+/// number value for that
+/// group
+/// ```
+///
/// # Notes on Implementing `GroupAccumulator`
///
/// All aggregates must first implement the simpler [`Accumulator`] trait,
which
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